The present invention concerns a centrifuge intended for manipulating liquids on an analytic scale, and consists of a body rotatable about its axis, this body comprising volumes in which separation of the liquid batch into components with different densities takes place, and conduits along which the liquid batch can be conducted into said volumes, so that the components of the liquid batch can be removed therefrom.
In manipulating small liquid batches on a laboratory scale, it is highly common practice to use centrifuges in which the liquid batch one wants to centrifuge is placed in a test tube. In such a case the placing of the liquid batch in the test tube and the removal of its components therefrom upon the conclusion of the centrifuging are mainly accomplished by manual labor. Also known in the art are centrifuging installations intended for manipulating larger liquid quantities in which the volume in which separation of the liquid into components takes place have been provided with conduits by which the liquid can be conducted into these spaces and its components can be removed therefrom upon the conclusion of the centrifuging. By using such apparatus, for instance, blood has been manipulated for separating the valuable blood plasma from the red and white cells.
Along with the advent of automatic analytic apparatus in clinical chemistry, the need has arisen to provide a centrifuge by which it would be possible to carry out the separation of small liquid batches into components, automatically by electronic control. The liquid batches to be manipulated would in the first place be blood samples, in which the plasma which constitutes the basis of the analyses must be separated from the red and white cells, which are irrelevant to the analysis. Therefore the centrifuge should comprise volumes in which the liquid, such as blood for instance, becomes divided into its components, an input conduit along which the liquid can be conducted into said volumes by electronic control, and a draining conduit by which the valuable component of the liquid, such as the blood plasma, is upon conclusion of the centrifuging under electronic control removable from the volumes, while at the same time the other components, such as the red and white cell masses, remains in its place.
The object of the present invention is to construct a centrifuge representing the analytic order of magnitude, i.e., one which is appropriate for manipulating liquid batches having a size between about 1 .mu.l and 100 ml, by the aid of which the above-mentioned objective is achieved. It is characteristic of the invention that in the body constituting the centrifuge there are two parallel volumes shaped like a circular arc and located at different distances from the axis of the body constituting the center of curvature. The volumes communicate with each through a narrow gap so that as the body is rotating, heavier components of the liquid batch accumulate in the volume at a greater distance from the axis and the lighter components accumulate in the volume closer to the axis, whereafter one of these volumes can be emptied through a conduit, while at the same time the surface tension acting in the gap between the volumes keeps the liquid in the other volume in its place.
It is advantageous to construct the centrifuge of the invention so that it consists of a disk-like body in which the parallel volumes, in which separation of the liquid into its components takes place, have been formed to be concentric rings running around the body along its peripheral part and interrupted at one point, and in which input and output conduits for the liquid and for its components connect with the body on its cenytral axis, which constitutes the center of said rings, and run inside the body radially to the volumes in the peripheral part of the body.
When one component of the liquid is removed from the centrifuge after centrifuging, removal takes place from that volume of the centrifuge where the ends of the input and output conduits are located. When the centrifuge is intended to be used in manipulating blood samples, the ends of the conduits have to be located in the inner volume, that is the volume which lies closer to the axis of the body constituting the centrifuge, in which volume the plasma--being the ligher component of blood--accumulates in the course of centrifuging. Furthermore, in a centrifuge for blood samples, the volumetric proportion of the inner volume and the outer volume should be about 1:2, corresponding to the quantitative proportion of plasma and of red and white cells in blood.
An essential feature in view of the functioning of the centrifuge of the invention is the shaping of the parallel, circular arc-shaped volumes and of the gap therebetween so as to enable one volume to be emptied of the liquid present therein while the liquid in the other volume remains in its place. The shaping should, moreover, be such that the latter volume can also be caused to empty itself when the differential pressure between the input and output conduits associated with the volumes is sufficiently increased. In the case where the emerging liquid is waste, the emptying of said volume may be connected with the cleaning of the volumes, subsequent to centrifuging, with a suitable washing liquid and with compressed air.
It is advantageous to shape the parallel, circular arc-shaped volumes of the centrifuge so that they have a cross section resembling a cup and between them is left a similarly circular arc-shaped ridge over which there is a gap connecting the volumes substantially over their entire length. The height of the ridge is preferably such that the gap lies higher than the volumes, by which is avoided any remixing of the components upon conclusion of the centrifuging.